IGroup
of Study and Research on Metabolism, Nutrition, and Exercise, Center of Physical
Education and Sports. Londrina State UniversityIIInstitute of Bioscience, Department of Physical Education. Paulista
State University  Rio Claro, SP

The magnitude of
men and women's neuromuscular, metabolic, and morphologic responses seems to
be quite different even when both are submitted to exercise protocols using
similar weight exercises protocols. However, differences in the motor performance
between men and women have been predominantly reported in protocols based on
isometric and isokinetic contractions. Thus, this study aimed to analyze men
and women's behavior during multiple sets of weight exercises achieving the
exhaustion, and later verifying possible differences as to the physical performance
between genders using weights with similar intensity. For this, 83 subjects
(50 men, and 33 women), 48 hours after being submitted to 1-RM tests in bench
press, squat and arm curl performed a protocol composed by four sets at 1-RM
80% up to achieving the exhaustion in each of three exercises to evaluate the
endurance ability to the fatigue in different muscular groups. It was used the
ANOVA and ANCOVA for repeated measurements, followed by the Tukey's post
hoc test, where P < 0.05 to the data treatment. It was verified
a significant fall in the performance both in men and in women since the first
up to the fourth sets of every exercise investigated (P < 0.01). Although
the fatigue magnitude was higher in men in all the three exercises, the effect
on the gender was only identified in the arm curl exercise (P < 0.01).
The results of this study indicated that men and women presented quite different
behavior in multiple sets of weight exercises, and women presented a more stable
performance and a higher endurance ability to the fatigue in the arm curl as
well.

The constant practice of weight exercises has attracted men
and women of different ages and of several levels of physical
skills related to the health, such as strength and muscular
endurance.

This fact is highly justifiable because of the scientific
knowledge advancement in the area of weight training (WT), mainly
in the last two decades, and this can be verified through the
high number of publications available in the literature
emphasizing the countless benefits coming from the practice of
such exercise, including those to treat cardiovascular diseases,
non-insulin dependent diabetes mellitus, obesity, and
osteoporosis, among other health problems that may affect the
human body along the lifetime.

Despite of this, there are still a few controversies involving
the way WT programs are mounted, once different combinations
among major variables related to such kind of training (number of
exercises, order of execution, number of sets and repetitions,
velocity of execution, recovery interval between sets and
exercises, weekly frequency) may propitiate quite different
responses.

It is worthy to point out that the magnitude of the response
to the WT can also be influenced by the gender factor, once the
information available in the literature has indicated that the
majority of women present lower values of muscular strength than
men both in the upper and in the lower limbs(2),
although such differences are quite attenuated whenever
comparisons between genders are conducted according to values
related to the body mass(3,4). Furthermore, the
plasmatic concentrations of the main anabolic hormones
(testosterone, GH and IGF-1) in rest or after intense struggle
are quite distinct in men and women(5,6).

Thus, another point that deserves to be clarified is that when
men and women are submitted to similar WT programs, they present
higher or lower tolerance to high intensity repetitive strength.
So, the initial purpose of this study was to analyze men and
women's behavior performing multiple sets of weight exercise in
different body segments, and later, to verify possible
differences of the physical performance between genders in
exercises performed under similar intensity.

METHODOLOGY

Subjects

Eighty-three apparently healthy college students (50 men, and
33 women) participated spontaneously in this study. As initial
criteria to the inclusion, participants should present mild
activity (constant physical activity < twice a week), and they
would have not participated in any regular physical exercise
program during the last six previous months of the beginning of
the experiment. Furthermore, previously to the beginning of the
study, each participant answered a questionnaire on his (her)
health history with no report of metabolic or muscular-skeletal
malfunction.

After being previously clarified on the purposes of the
investigation and related procedure they would be submitted to,
every participant signed a free and clarified consent term. This
study was approved by the Ethic Committee Research of the
Londrina State University according to the rules of the National
Council of Health's Resolution 196/96 on researches involving
human beings.

Anthropometry

The body mass was measured in an 100 g precision and maximum
load of 180 kg Urano digital scale model PSI80 A,
and the stature was determined in an 1 mm precise wooden
stadiometer, according to procedures recommended by Gordon et
al.(7). From these measurements, the body mass
index (BMI) was calculated by the ratio between the body mass and
the square of the stature, the weight was expressed in kilograms
(kg), and the stature was expressed in meters (m).

1-RM tests

The muscular strength was determined by means of the maximum
repetition test (1-RM) in three exercises involving segments of
the trunk, the lower and upper limbs. The order of execution of
the exercises tested was respectively: bench press, squat and arm
curl. The interval between exercises was of at least five
minutes. These exercises were chosen since they are quite popular
in training programs using weights in subjects with different
training levels.

Prior to the beginning of the tests, in each sequence of three
exercises subjects were submitted to a warming sets (6 to 10
repetitions) with approximately 50% of the estimated load in the
first try of the 1-RM test. The testing initiated two minutes
after the specific warming. Subjects were oriented to try
completing two repetitions. In case two repetitions were
completed in the first try, or even if it was not completed a
single repetition, it was performed a second try after a recovery
interval of three to five minutes with a higher load (first
possibility) or lower load (second possibility) to that used in
the previous try. This procedure was repeated once again in a
third and last try in case the load related to a single maximum
repetition was not determined yet. Therefore, the load recorded
as 1-RM was the one when it was possible to the subject to
complete a sole maximum repetition(8).

Prior to the beginning of the study, it was employed a
familiarization protocol, trying to reduce the learning effects,
and to establish the reproducibility of the tests in the three
exercises. All subjects were tested in similar situation to the
protocol adopted in six different sessions, with intervals of 48
hours. The intra-classes coefficient (R) was of 0.98 in the bench
press exercise, and 0.96 in the squat and arm curl exercises.

It is worthy to mention that the way and execution technique
of each exercise was standardized and continuously monitored,
trying to assure the efficiency of the test.

Fatigue evaluation protocol

A protocol to evaluate the fatigue endurance ability was
applied between 48 and 72 hours after the last six sessions of
the 1-RM tests in the three exercises previously described. The
order of execution of exercises of the protocol was identical to
the one adopted during the 1-RM test.

The protocol was composed by the execution of four sets of
each exercise at 80% 1-RM up to the voluntary exhaustion.
Subjects were oriented to try to execute the maximum possible
repetition in each sets, until they reached a functional
incapacity to surpass the resistance offered. The recovery
interval between sets was of two minutes, and in different
exercises, the interval was of three to five minutes.

The three exercises were preceded by a warming sets in the own
equipment, with a 6 to 10 repetition with an approximately 50%
load set for each exercise.

The rate of the declining strength between the first and
fourth sets of each exercise was used as the fatigue index,
according to the equation proposed by Sforzo and
Touey(9) below:

FI
= [(TS(1st sets) TS(4th sets)/TS(1st sets)]
* 100%

where FI = Fatigue Index and TS = Total Strength (load lifted
x number of repetitions executed during the sets).

Statistical treatment

The t Student test for independent sampling with
different number of elements was used to compare men and women's
general features. It was used the variance analysis (ANOVA) 2x2
for repeated measurements, to compare genders (men and women) in
different sets of exercises. To those variables where the initial
conditions of groups were statistically different, it was used
the covariance analysis (ANCOVA), along with the baseline adopted
as co-variables. It was employed the post hoc Tukey's test
for multiple comparisons to identify specific differences in
variables in which the F values found were higher than the
statistical significance set (P < 0.05).

RESULTS

Table
1 it presents the general features of the subjects investigated. The body
mass of men was significantly higher than the one found in women (12.7 kg, or
22%; P < 0.01), as well as the stature (13 cm, or 8%; P <
0.01). It was found no significant differences in the BMI values compared to
both genders (P > 0.05).

The absolute values
of the lifted load during the 1-RM tests in the bench press, squat and arm curl
exercises of men ad women are presented in table 2. In the
three exercises, women presented a lower performance compared to men's. Thus,
women reached around 47% of the load lifted by men in the bench press exercise
(P < 0.01), ~57% in the squat exercise (P < 0.01), and ~54%
in the arm curl exercise (P < 0.01).

Whenever comparisons
between men and women's performance in 1-RM tests were set based on the body
mass, differences were reduced; however, they have kept statistical significance
(figure 1). In such sense, values of the muscular strength
related to the body mass found in women were of ~58% in the bench press (P
< 0.01), ~68% in the squat (P < 0.01), and ~65% in the arm curl
(P < 0.01) of those reached by men.

The number of repetitions
performed by men and women in strength resistance tests (1-RM 80%) in the first
and fourth sets of the three exercises investigated is presented in table
3. It was verified a significant decrease in the motor performance in every
exercise analyzed between the first and fourth sets (P < 0.01) both
in men and women, although the effect of the gender factor was identified only
by ANCOVA in the arm curl exercise, with women presenting a lower fatigue index
(FI) than men (P < 0.01). It was found no sets x gender interaction
in any of the exercises studied. Figure 2-4 present a more
detailed analysis on men and women's behavior during the four sets performed
in the bench press, squat, and arm curl exercises.

DISCUSSION

Several studies of the literature investigated the motor
performance of men and women in isometric, isokinetic, and
dynamic contractions, as well as the endurance ability to the
fatigue. This study analyzed men and women's behavior in multiple
sets of exercises performed using free weights in different body
segments (upper limbs, trunk, and lower limbs), and possible
sexual differences in the endurance ability to the fatigue.

This investigation also identified differences in the muscular
strength between genders both in absolute and relative terms in
every exercise analyzed, and men presented higher values than
women in 1-RM tests. Although our findings have strengthen
information available in the literature, the magnitude of
differences found between genders in different studies have been
quite different, and this can be at least in part explained by
several factors, such as: type of exercise performed, body
segment evaluated, levels of physical ability of the subjects
investigated, equipments used (free weights or machines), type of
maximum voluntary contraction employed (concentric and/or
eccentric).

On the other hand, several studies using maximum voluntary
contractions or using electromyography have indicated a higher
tolerance to the struggle in women(10-13).

Despite the previous investigations indicate that the higher
women's capacity to resist to the fatigue seems to decrease
according to the need of struggle increases or even that women
present a higher endurance ability to the fatigue only in
sub-maximum struggle performed under intensity up to 70% of
maximum voluntary contraction(14,15), our study
indicated that such fact can also be noted in strength performed
at an intensity equivalent to 1-RM 80%.

In such sense, women presented a lower performance decrease
than men's in the three exercises investigated, although the
effect of the gender has been statistically confirmed only in the
arm curl exercise (P < 0.01).

It is worthy to mention that trying to assure the quality of
the information obtained from 1-RM tests applied in the three
exercises investigated, every subject was submitted to six
testing sessions, in order to be familiarized with the demanded
procedures. It is believed that the adoption of such procedure
may have reduced considerably the possibility that the loads,
mainly in females, have been underestimated in the fatigue
resistance protocol (1-RM 80%).

Another aspect that deserves our attention is that the
majority of the researches available in the literature on the
ability to resist to the fatigue has been using protocols
involving isometric or isokinetic contractions, and this is
substantially different from the information produced by this
study, once exercises were performed before dynamic, concentric
and eccentric contractions.

Although the possible mechanisms to explain the gender related
differences as to the capacity to resist to the fatigue is not
yet clearly set by the literature(10), it is believed
that differences in the muscular mass upon the use of substrates,
in the muscular morphology or even in the muscular activation
between men and women should be analyzed more judiciously, trying
to explain such phenomenon.

Furthermore, changing the proportion of the types of muscular
fibers between men and women may interfere in the capacity to
resist to the fatigue, once in general terms, women present lower
differences in the proportion between type I and II fibers
compared to men(16), and this can help to increase the
capacity to resist to sub-maximum struggles for extended periods
of time.

It is important to point out that in this study the decreasing
rate of the motor performance was merely estimated by the
difference between the number of repetitions performed in the
first and last sets in each of the three exercises analyzed,
according to the mathematic model proposed by Sforzo and
Touey(9). In such sense, this study did not succeed to
answer whether there is any physiological or biochemical
difference able to justify such different behavior between
genders.

Another interesting feature observed was that both men and
women presented a higher fall in the performance of the first
exercise (bench press) compared to the second one (squat), and
from this one related to the third one (arm curl). This indicates
that the fatigue generated by the first exercise of the sequence
do not seems to be negatively reflected on the performance of
other exercises, when the requested muscular groups are different
from those previously demanded. However, it remains to be
clarified if a changing in the order of execution of exercises or
even if they re performed solely (in different days) would cause
a similar behavior to that found in this investigation.

Another important finding in this study is that the number of
repetitions related to the 80% intensity of 1-RM was not
preserved in none of the exercises tested along with the four
sets performed, and this seems to risk the training prescriptions
based on 1-RM percentages to develop the muscular strength,
potency, muscular endurance, and mainly hypertrophy recently
suggested(1).

Furthermore, the number of repetitions executed in the first
sets by men and women was relatively different in each exercise.
This information strengthen what was found by Hoeger et
al.(20,21) indicating that the strength based on
the 1-RM percentage would not be the better way to prescribe
exercise programs using weights, once the number of repetitions
performed in sole sets of different exercises can oscillate quite
pronouncedly, even when the struggle intensity is similar, such
as that used in the present investigation (1-RM 80%).

CONCLUSIONS

The results in this study indicated that men and women
presented relatively different behavior in multiple sets of
weight exercises, and women presented a more stable performance
and a higher capacity to resist to the fatigue, mainly in the arm
curl exercise.

Both the number of repetitions performed in the first sets of
each exercise and the total number of repetitions performed along
the four sets seems to be variable according to the motor duty
demanded and the gender.

The decreasing performance verified in this investigation was
higher in the first exercise of the sequence in both genders, and
this indicates that the fatigue generated in the beginning does
not seem to compromise the execution of the other sequential
exercises when the muscular groups demanded are different.

Despite the results of this study indicate a significant
performance decrease when men and women are submitted to multiple
sets of weight exercises, as well as the mechanisms responsible
by the differences in the endurance ability to the fatigue of men
and women still deserve to be further investigated.